"This is the first reported case of an urticarial rash apparently caused by the frustration of watching England play football."

With these words, written in 1987, a London GP trainee named P Merry alerted readers of the Journal of the Royal Society of Medicine to a little-suspected risk of rooting for a World Cup team. Rooting can cause emotional upset, which can cause urticaria. Urticaria is also known as "hives".

Here's what happened: "When Portugal scored the only goal of the match to win 1-0, he became extremely upset, and developed the rash of urticaria on his trunk and limbs. This persisted for 36 hours and then settled." Four days later, the man watched England v Morocco. "When a member of the English team was sent off, he became agitated and subsequently developed the same rash."

Recently, 34-year-old Paul Hucker, of Ipswich, Suffolk, made headlines when he bought an insurance policy against the possible trauma of a defeat for England in the World Cup. Many people chuckled at the news. A wander through the medical literature suggests they should temper their amusement.

Five researchers at the University of Bristol published a warning in 2002, in the British Medical Journal, that "myocardial infarction can be triggered by emotional upset, such as watching your football team lose an important match".

Their main evidence: hospital statistics collected at the time of the 1998 World Cup. "Risk of admission for acute myocardial infarction," the doctors point out, "rose by 25% on June 30 1998 [the day England lost to Argentina in a penalty shoot-out] and the next two days."

Four researchers in Lausanne, Switzerland, say a similar thing happened during the 2002 World Cup. They tell their tale in the International Journal of Cardiology. The number of sudden cardiac deaths was 63% higher during the World Cup than during the same period a year earlier. The doctors try to analyse it: "We explain this by an increase in mental stress and anger and possible unhealthy behaviour (greater alcohol and tobacco consumption, decreased medical compliance) of supporters. The lethal effect of mental stress and anger has been attributed to its activation of the sympathetic nervous system leading to hypertension, impaired myocardial perfusion in the setting of atherosclerotic disease and a high degree of cardiac electrical instability precipitating malignant arrhythmias."

Fandom carries danger, yes, but there's a special payoff for those whose team does capture the ultimate glory. Or so implies a study that appeared in 2003 in the journal Heart. Written by two French doctors, the title proclaims: "Lower Myocardial Infarction Mortality in French Men the Day France Won the 1998 World Cup of Football."

(Thanks to Reto Schneider for bringing the urticaria to my attention.)

· Marc Abrahams is editor of the bimonthly magazine Annals of Improbable Research (www. improbable.com) and organiser of the Ig Nobel Prize